SYNOPSIS

DESCRIPTION

The posix_mem_offset() function shall return in the variable pointed to by off a value that identifies the offset
(or location), within a memory object, of the memory block currently mapped at addr. The function shall return in the
variable pointed to by fildes, the descriptor used (via mmap()) to establish the
mapping which contains addr. If that descriptor was closed since the mapping was established, the returned value of
fildes shall be -1. The len argument specifies the length of the block of the memory object the user wishes the
offset for; upon return, the value pointed to by contig_len shall equal either len, or the length of the largest
contiguous block of the memory object that is currently mapped to the calling process starting at addr, whichever is
smaller.

If the memory object mapped at addr is a typed memory object, then if the off and contig_len values
obtained by calling posix_mem_offset() are used in a call to mmap() with a file
descriptor that refers to the same memory pool as fildes (either through the same port or through a different port), and
that was opened with neither the POSIX_TYPED_MEM_ALLOCATE nor the POSIX_TYPED_MEM_ALLOCATE_CONTIG flag, the typed memory area that
is mapped shall be exactly the same area that was mapped at addr in the address space of the process that called
posix_mem_offset().

If the memory object specified by fildes is not a typed memory object, then the behavior of this function is
implementation-defined.